When your opening hand has seven Lands it is time to mulligan, but what you do with your hand and your Library at that point can be the difference between a keeper at six, and a mulligan down to five. It's fairly common practice in my playgroup to 'mana-weave' or 'mana-shuffle' a deck before a game, where one evenly distributes the land cards among the spells. In a twenty-Land deck of sixty cards, that's a very straightforward order of Spell, Spell, Land repeated. What is often overlooked, however, is that this practice is tantamount to stacking your deck, and by no means constitutes a random ordering of the cards, regardless of whether you know where each spell is in your deck. In a truly random deck there is no need to mana-shuffle, and you can avoid the issue entirely by using sufficiently randomizing shuffling techniques. While it seems a bit counter-intuitive, your Magic deck should perform most consistently when it is random. After all, it is designed with randomness in mind.
When you mana-shuffle your deck as above, you are ordering the cards in such a way that it is very straightforward to separate the lands again. A three-pile pile shuffle, where you separate the cards face-down into piles, can clump every land in your deck together. Similarly, with the deck as-is, the first and thirty-first cards are both lands, since the three-card cycle will repeat at thirty, exactly halfway through the deck. A perfect riffle shuffle will eradicate your work and ensure that your lands are now in clumps of two throughout the deck. Now we've got a six card cycle, instead of three cards, which also happens to repeat at thirty. One more perfect riffle shuffle and you've got clumps of four lands, distributed evenly throughout the deck. Four lands and eight spells gives a cycle of twelve, so further shuffling should, in theory, start re-randomizing your deck, but take this as a lesson that mana-shuffling, followed even by real randomization, can cause some major issues in your land distribution. To be fair, if you can perform perfect riffle shuffles like this, you probably already know more than I can possibly tell you about card ordering, but even to novice shufflers, I hope this will serve as a warning. If you must mana-shuffle, be very sure to thoroughly randomize your deck afterwards, lest you end up causing exactly the problem you were trying to avoid.
Now we've uncovered some interesting tidbits about mana-shuffling, and I expect that I'll be avoiding that practice entirely in the future, the question that presents itself is "How should I shuffle?" Variety seems to be the consensus on that. While it has been said that a deck of 52 cards can be randomized with seven to eight riffle shuffles (3/2log2n), using a variety of shuffling techniques can help to ensure that even your imperfect riffles can actually yield a mostly-random deck of cards. This Deck Tech article suggests a combination of pile and riffle shuffling, where you actually shuffle the piles from your pile shuffle together using a riffle, to further randomize the results. Along these lines, I'd like to introduce mash shuffling for those of us using sleeves who lack the proficiency to actually riffle shuffle with sleeved cards. Mash shuffling takes two stacks of cards, preferably sleeved, and pushes them together along the edge, to some general approximation of a riffle shuffle. It's a bit less effective, in my experience, than true riffle shuffles, but a sufficient number of mash shuffles should still yield an adequately random stack.
One thing that comes up periodically is the idea of shuffling too much, which is, as it turns out, not as far-fetched as it might seem. Assuming that you do perfect in-shuffles or out-shuffles, then you can, in fact, re-order the cards to their original configuration. As per Wolfram, performing only in-shuffles, you'd have to shuffle fifty-two times to get back to the original. Out-shuffles, however, require only eight for a fifty-two card deck. Of course to be able to perfectly riffle shuffle this many times in a row requires a lot of practice, so unless that's what you're going for, you probably don't have to worry about it.
When all is said and done, your best bet for a mostly-randomized stack of cards is to combine multiple shuffling methods and shuffle thoroughly. Pile shuffle (this also allows you to count your cards before each game, which is typically suggested,) then riffle or mash shuffle the piles together, then riffle or mash shuffle the whole mess seven or eight times intermingled with overhand shuffles, then let your opponent shuffle. At last, you'll be as close to random as one can realistically expect.
A: The controller of the Wurmcoil Engine gains 6 life. Even though the MIrran Crusader's Toughness is only 2, the Wurmcoil Engine still assigns 6 damage to the Crusader because it has 6 Power. This will mark 6 damage on the Crusader which will be destroyed the next time State-Based Actions are checked.
119.3f Damage dealt by a source with lifelink causes that source's controller to gain that much life, in addition to the damage's other results.
510.1a Each attacking creature and each blocking creature assigns combat damage equal to its power. Creatures that would assign 0 or less damage this way don't assign combat damage at all.
Question of the Week
During Combat, what step is the last opportunity you have to animate an Inkmoth Nexus to allow you to use it to block an attacking creature?